Why antibiotics aren’t effective

As the world braces for its worst ever threat in the last century - global antibiotic resistance due to unnecessary and unregulated popping of antibiotics, an average Indian has been found to be popping over 11 antibiotic pills a year.For 50 years, hospitals have used a single test to decide how to treat the most stubborn infections. But according to a growing body of research, that test is now wrong more often than we’d thought.

All because of the rise of antibiotic-resistant bacteria that behave one way in lab tests and another way in the human body. The findings have huge implications for how doctors fight the growing problem of so-called superbugs, which can’t be easily treated with antibiotics. The bacteria infect 2 million people each year in the US alone, and kill 23,000, according to the Centers for Disease Control.

“We’re saying the standard way the world does this is wrong,” said Michael J Mahan, a professor of microbiology at the University of California, Santa Barbara. That standard protocol, established in the 1960s, is called antibiotic susceptibility testing: Bacteria are grown in a solution called Mueller-Hinton broth, and then attacked with various antibiotics to see which one works best.

Doctors around the world use the test to decide which antibiotic to use for which bacterial infection. But Mahan in August published an article in the journal EBioMedicine that shows blind spots in the protocol, which hasn’t changed much since it was instituted as the gold standard across medical labs several decades ago. When his team tested salmonella in the petri dishes that labs typically use, an antibiotic called polymyxin killed the bacteria. But when they grew salmonella in petri dishes formulated with a material that more closely resembles the cells the bacteria infect, the antibiotic was useless.

They concluded that the bacteria’s defences — essentially the mechanisms that make superbugs “super”— can switch on or off depending on their surroundings. The salmonella had turned on its superpowers. Another recent study led by Victor Nizet, a professor of pediatrics and pharmacy at UC San Diego, showed a similar result.

The antibiotic susceptibility test is also how pharmaceutical companies evaluate the effectiveness of potential new drugs. Mahan and Nizet haven’t tested their findings in human patients yet. But what they’ve identified is consistent with anecdotal reports from doctors. Mahan said his findings have immediate implications for doctors who encounter stubborn infections: “If the drug doesn’t work, switch the drug.”